Copper alloy



Patented July 7, 1936 UNITED STATES PATENT OFFICE COPPER ALLOY- sylvania No Drawing. Application December 20, 1934,

Serial No. 758,439

4' Claims. (01. 15-154 This invention relates to alloys and particularly to alloys of copper and other metals that form a solid solution in copper.

The copper which is utilized as conducting 5 components in electrical machines, such as commutators and slip rings of rotating electrical machines, does not have 1 high mechanical strength and as it sometimes becomes necessary for it to support considerable loads, temporary deformations sometime occur as the temperature rises which impair the balance or alinement of the machine and adversely afiects its smooth operation under load. These temporary deformations are caused by a low resistance to del' ormation at working temperatures. This misalinement is particularly troublesome in cominutators which operate at temperatures of 100 to 150 centigrade under full load because the deformation of the commutatorbars or plates is accompanied by arcing and other defects generally described as poor commutation.

An object of this invention is to provide an alloy of copper and other. metals which have excellent physical properties at the operating temperatures of dynamo-electric machines and which also has good thermal and electrical conductivity.

Another object of this invention is to provide A a ternary alloy of copper and other metals which are capable within the limits of their solid solubility in copper of increasing, after cold working, the resistance of the alloy to deformation at elevated temperatures.

A further object of this invention is to provide a ternary alloy of copper and other metals which, when subjected to cold working, will have a a high recrystallization temperature.

It is generally assumed that the mechanical properties of copper are the same at temperatures of 100 to 150 centigrade as at atmospheric temperature. It has been discovered, however, that the plastic deformation in per cent of the applied strain at normal loads isgr'eatly affected by increasing the temperature of copper from 25 centigrade to 100 centigrade. This increase in theplastic deformation is particularly responsible for the failure of the ma chine parts to maintain their initial relative po- 50 sitions while in service. It is therefore desirable to utilize a metal which has a high recrystallization temperature as the component parts of rotating electrical machines, since it has been discovered that the recrystallization temperature, 55 after the cold working, is a measure of the resistance oi the alloy to plastic deformation at moderate loads.

In practicing this invention, certain alloying metals are added to copper to produce a copper alloy which will have excellent physical prop- 5 erties, a high recrystallization temperature and good conduct'vit'y. The proportions of the metals which are added to the copper melt are maintained within the limits of their solid solubility in the copper and are not present in such pro- 10 portions as to decrease the conductivity of the resulting alloy to an undesirable value. As a rule, the content of each of the alloying metals which are added to the copper melt is maintained between .05% and 5%. 15

The alloy comprises copper, silver and tin. The silver content of the alloy may range from .05% to .5% while the tin content ranges from .2% to .5%. The balance of the alloy is copper and such nominal impurities as are present in 20 electrolytic copper or as remain after effective deoxidization of the melt.

While the silver content is given as .05% to .5%, it is preferred to maintain the silver content between the limits of .05% to 25%. Silver 25 in amounts above 25% does not enter into solid solubility with the copper and therefore has little if any influence on the recrystallization temperature of the resulting alloy. It can be generally stated that the upper limit on the silver 30- content is imposed by its restricted solid solubility in copper.

Tin is employed as an alloying constituent because it supplies the greatest hardening eflect for unit loss in conductivity of the alloy and in- 35 creases the recrystallization temperature 01' the alloy. The silver addition, within the limits hereinbefore described, further increases the recrystallization temperature without severe loss in conductivity. A preferred alloy having the de- 40 sired characteristics and within the preferred range of alloying content comprises .4% tin, 2% silver, with the balance copper and such nominal impurities as are present in electrolytic copper or that remain'aiter the eifective deoxidization of the melt.

The alloy may be prepared in the usual manner such asby melting the copper and adding the silver and tin in the desired amounts, casting the alloy, and then rolling or drawing the cast alloy into the desired shapes and sizes. The alloy may or may not be deoxidized depending upon whether or not the additional hardening efiect of copper oxide is desired. In order to increase the hardness of the alloy it has been found desirable to cold roll the alloy with a reduction of from 10% to 85% depending upon the results desired.

As compared to pure copper which has been cold worked 80%, alloys produced in accordance with the teachings of this invention and cold worked in the same manner have a much'higher recrystallization temperature with only a small increase of resistivity. 'The pure copper has a recrystallization temperature of 180 centigrade and a resistivity of 1.74 microhms per cubic centimeter, while the alloy of copper, silver and tin has a recrystallization temperature of above 250 centigrade and up to approximately 435 centigrade and a resistivity of between 1.8 and 2.5 microhms per cubic centimeter depending upon the silver and tin content of the alloy.

From these results it is evident that the resistance of the alloy to plastic deformation will be greatly increased by the small addition of the alloying metals, silver and tin, within their limits of solid solubility in copper and that the resulting alloy will have excellent physical properties at normal operating temperatures of 100 to 150 centigrade.

It is, of course, to be understood that various modifications may be made in the alloying content as above described without in any way departing from the spirit of the invention and scope of the appended claims.

I claim as my invention:

1. An alloy comprising from about 0.2% to 0.5% tin, from about 0.05% to 0.5% the balance copper.

2. An alloy comprising from about 0.2% to 0.5% tin, from about .05% to 0.25% silver and the balance copper.

3. An alloy comprising .04% tin, 0.2% and the balance copper.

4. An alloy comprising from about 0.2% to 0.5% tin, from about .05% to 0.25% silver and the balance copper which has a resistivity of between 1.8 and 2.5 microhms meter.

HOWARD SCOTT.

per cubic centi- 2 silver and 10 silver 15 

